Why the Stone hammer Technology
The rural areas of developing countries face an increasing demand for water, both for domestic purposes and irrigation. However these countries have often underground water reserves that could be used in a sustainable way for irrigation. Besides knowledge of irrigation skills, the principal limiting factor is the high cost of wells to gain access to the groundwater. Practica recently identified a “new” well drilling technology, the so-called Stone hammer, that has the potential to substantially reduce the cost of well drilling in hard ground layers. The development of this technology started 3 years ago in India and was successfully introduced in Nicaragua in 2000.

Expected benefits

• A method for manual well drilling that can drill in harder ground layers and that is cheaper than other manual drilling methods

• A drilling technology that can be produced and used with local materials and skills.

• Increase food production by irrigation (food security) by adding a
  Low- cost option for manual well drilling.

• Contribute to local industry through the in-country manufacture of drilling equipment.

• Increase the efficiency and safety of manual well drilling for local well drillers.

The technology

Communal wells for drinking water are often drilled with high-tech equipment, funded and organized by local water departments and donor organizations like UNICEF, Care etc. However, many wells are domestic wells, made and used by one or several families. Traditionally these wells are made by “sludging” a small hole (tube well) of 8 to 15 cm diameter or digging a bigger hole by hand with a diameter of 1 to 1.5 meters.
Especially the construction of hand-dug wells deeper than 5 meter is a time consuming, costly and often a dangerous activity..
To make low-cost tube wells, there are several hand drilling technologies available around the world. For instance the sludging method in India or the bailer and pulse technology as developed by DHV in Tanzania. Also there is the rotative hand drilling technology as used in Zimbabwe or more recently the EMAS method (using a mud pump) developed by GTZ in Bolivia. However all these technologies have the limitation that they cannot drill through hard layers like consolidated soil formations or ”tuff” stone. This presents a serious limitation in countries like Nicaragua where some 80 % of the water layers at 10 to 30 meter deep only can be reached if hard layers of 1 to 5 meter thick are passed.

New drilling technology

Recently a technology was developed that has better potential to drill through harder soil formations than the drilling technologies mentioned before. This is the so called ”Stone hammer” a technology that was developed in the North Bengal Terai Development project in India by Arcadis Euroconsult.
The first experiences indicate that, compared to hand-dug wells, the Stone Hammer has the following advantages:

• Some 40 % cheaper ( $600 versus $1000 for a 20 meter well)

• Better water quality because of deeper penetration in the aquifer

• Less accidents during construction

• Less risk of contamination of the water

A drilled well is easier to cover so less risk of damage in case of mud floods (like happened with the hurricane “Mitch”)                                                                        

The advantages of the Stone hammer compared to machine-drilled wells are:

• Cheaper because of input of local labour. ($600 versus $1500)

• Much simpler, less maintenance problems (No “high-tech” parts like carburretor, gearbox etc.)
  Compared to machine drilled wells a draw back of the Stone hammer is that it is slower.

  4. Current status

After the “Indian Stone hammer” was adapted in Nicaragua, a first set of drilling equipment was produced in Nicaragua and 5 wells were drilled in the pacific region. During these drillings several types of ground layers with different “hardnesses” were encountered. For some layers, the used technology proved to be successful, for instance a 10-meter deep well was drilled in 2 days. In other ground layers the well drilling took several weeks because drill bits were damaged. Another problem was that it is very time consuming to dismantle the tubes every time the drill is lifted. Therefore tubes and drill bits have to be adapted to improve quality and reduce time.
Also adaptations are needed that combine the sludging method with the Stone hammer technology. Extensive field test are needed to improve durability and standardize the technology to make it suitable for local production and further implementation.

Hand- sludge drilling in Nicaragua.